In one type of conventional unused film cartridge, film is wrapped around a spool within the cartridge, and the end of the film extends from the cartridge to facilitate loading of the film into a camera. To load the film, the camera is opened and the cartridge is inserted into a cartridge compartment in the camera. The end of the film is then grabbed by the user and placed into the film track. When the camera is closed, the film is pulled from the cartridge frame by frame and rolled onto a take-up spool, as is generally known in the art.
Recently, a new type of film cartridge, a "thrust cartridge", has been developed wherein the film is capable of being thrust out of the cartridge by rotating the cartridge spool in the appropriate direction. This feature allows the film within a cartridge to be completely enclosed within the cartridge, rather than having the end of the film extending therefrom. In addition, partially used film can be rewound into the cartridge and then used at a later date by thrusting the film from the cartridge and advancing the film to the next unexposed frame. Specifics regarding the structure and operation of one type of thrust cartridge can be found in commonly-assigned U.S. Pat. No. 5,231,438, to Smart, which is incorporated herein by reference in its entirety.
When loading thrust cartridges, the cartridge is placed into the camera and the camera door is closed to prevent light from entering the camera and exposing the film. The cartridge spool is then rotated in the appropriate direction to thrust the film from the cartridge and through the film track. Once the film reaches the end of the film track, it is engaged by the take-up roll. Thereafter, a transfer of drive power occurs between the cartridge spool and the take-up spool. That is, the thrusting of the film by the cartridge spool is deactivated, and further movement of the film is provided by a pulling action of the take-up spool. When rewinding of the film into the cartridge is desired, drive power is provided by the cartridge spool by rotating the cartridge spool in the appropriate direction to rewind the film.
U.S. Pat. No. 5,287,136 to Kitagawa et al. discloses a camera that automatically advances and rewinds a thrust film cartridge. To thrust film from the cartridge, a controller directs a motor to drive the cartridge spool in the advance direction to thrust film from the cartridge. Once the film is advanced into engagement with the take-up spool, the controller actively directs the motor to stop driving the cartridge spool and to commence driving the take-up spool. When rewind of the film is desired, the controller directs to motor to stop driving the take-up spool and to commence driving the cartridge spool in the rewind direction. To perform the various drive functions, the described camera utilizes a combination of a reversible motor, two on/off clutches, and a controller for selectively activating and deactivating the motor and the clutches. Such use of expensive electronic components essentially limits the use of such a device to high-end automatic cameras.
With the recent popularity of inexpensive, manually-wound cameras (e.g., single use cameras), it is typically desirable to design new camera mechanisms to be useable therewith. Accordingly, it can be appreciated that it would be desirable to provide a simple, inexpensive mechanism for rotating a thrust cartridge spool to thrust film from the cartridge, while also providing for take-up spool rotation to engage and advance the film. In addition, the cartridge spool should be rotatable in the opposite direction to facilitate rewinding the film back into the cartridge after a desired portion of the film is exposed.